postgresql 如何将点文本转换为几何图形
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How to convert point text to geometry
提问by Muneem Habib
I have installed postgis in my DB. Now i have 1 regions in my DB like ((-79.4609576808001,43.9726680183837)) I want this region to convert to geometry type. I have searched on google and found that St_geomfromText will convert text to geometry type.
我已经在我的数据库中安装了 postgis。现在我的数据库中有 1 个区域，例如 ((-79.4609576808001,43.9726680183837)) 我希望这个区域转换为几何类型。我在谷歌上搜索过，发现 St_geomfromText 会将文本转换为几何类型。
my query is as follows:
我的查询如下：
SELECT ST_GeomFromText(region,4326) from "erpAssets";
But it is giving error it is saying that no function matches for st_geomfromtext
但它给出的错误是没有函数与 st_geomfromtext 匹配
回答by John Powell
You can also use ST_MakePoint which is probably cleaner as you don't have to concatenate latitude and longitude values as text. Use it in conjunction with ST_SetSrid to set the coordinate reference system to 4326, eg,
您还可以使用 ST_MakePoint，它可能更简洁，因为您不必将纬度和经度值连接为文本。与 ST_SetSrid 结合使用将坐标参考系设置为 4326，例如，
Select ST_SetSrid(ST_MakePoint(lon, lat),4326) from sometable;
will return a geometry type. Note the order is lon/lat (x/y), a cause of lots of confusion, due to people saying lat/lon in everyday speech.
将返回几何类型。请注意，顺序是 lon/lat (x/y)，由于人们在日常讲话中使用 lat/lon，因此会引起很多混淆。
ST_GeomFromText is generally more useful when you have a geometry in Well-known text (WKT) format, eg,
ST_GeomFromText 通常在您拥有 Well-known text (WKT) 格式的几何图形时更有用，例如，
Select ST_GeomFromText('POLYGON((0 0, 10 0, 10 10, 0 10, 0 0))', 4326);
If your data is actually in the form ((-79.4609576808001,43.9726680183837)) and you don't want to split it up as I suggested above, the correct format to use use with ST_GeomFromText for a point is:
如果您的数据实际上是 ((-79.4609576808001,43.9726680183837)) 形式，并且您不想按照我上面的建议将其拆分，那么与 ST_GeomFromText 一起使用的正确格式是：
Select ST_GeomFromText('POINT(-79.4609576808001 43.9726680183837)', 4326)
where the SRID is optional, but recommended.
其中 SRID 是可选的，但建议使用。
See http://en.wikipedia.org/wiki/Well_Known_Textfor more information.
有关更多信息，请参阅http://en.wikipedia.org/wiki/Well_Known_Text。
回答by midfield99
It looks like ST_GeomFromText is expecting a string, not a variable. Is ST_GeomFromText better than providing direct geometry?mentions the function is immutable.
看起来 ST_GeomFromText 需要一个字符串，而不是一个变量。ST_GeomFromText 比提供直接几何更好吗？提到函数是不可变的。
This question gives one way of building a string from variables. Insert PostGIS Object (e.g. ST_GeomFromText) from row variables in plpgsql script
这个问题给出了一种从变量构建字符串的方法。 从 plpgsql 脚本中的行变量插入 PostGIS 对象（例如 ST_GeomFromText）
So it looks like Chris Traver's solution should work for you:
所以看起来 Chris Traver 的解决方案应该适合你：
ST_GeomFromText('POINT(' || row_data.longitude || ' ' || row_data.latitude ||
' ' || row_data.altitude || ')', 4326)
So you just need to access the x and y portion of the point.
ST_X(point)and ST_Y(point)will respectively return the x and y coordinate of a point in PostGIS, but I don't know what data type regionis, and I don't think it a point type.
所以你只需要访问点的 x 和 y 部分。
ST_X(point)并且ST_Y(point)会分别返回PostGIS中一个点的x和y坐标，但是我不知道数据类型region是什么，我认为它不是点类型。
